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Old 06-10-2013, 12:39 PM   #1
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Cam Deviation out of spec?

I hooked up a Durametric to my 2001 Boxster S and noticed that the Cam deviation was 6.4 on one bank and 4.7 on the other.

I think the specs allow 6 deviation so being that I'm out of spec I stopped racing.

Is this something I need to worry about, is being out of spec a serious issue with the engine timing?

For racing i'd rather bring it back into the good range and wonder what needs fixing in order to bring it back in line.

Any Ideas, suggestions?
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Old 06-10-2013, 01:39 PM   #2
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Mine is at 0 and 6 and I've been wondering about this as well. I'm still within spec and do monitor it. I figured when it came time for a clutch and ISMB that would be the time to tackle the cam chain tensioners, guides, and timing too. A timing kit (tools to lock cams, flywheel, etc.) is only about $350 or so on e-Bay. Biggest question I've had is where to find detailed instructions on retiming the engine and replacing all the individual components. Although I will admit I have not spent a LOT of time looking since it hasn't been a high priority.

I do know there are quite a few threads on it and the earlier 5 chain setup has been discussed, but I don't recall seeing a detailed how-to on it. A bit of searching here and on Rennlist might find what you are looking for though.
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Old 06-10-2013, 02:29 PM   #3
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here's a cool image:

http://www.pelicanparts.com/techarticles/Boxster_Tech/16-ENGINE-Camshaft_Swap_and_Chain_Tensioner/Gp1800.pdf

the short chains on each side are part of the vario-cam system that change the cam profile as rpm increases. in the image you can see the two pads that push on the chain and adjust the cams. these pads wear, especially on earlier cars. that rattle on start up - that's your chains slapping against the pads. you may have seen the hard green plastic bits in your oil filter - that's these pads. as a result porsche changed to a harder material and it's one of the upgrades you can do to your car - use the later pads. they are cheap, but the work to get at them isn't. the deviation info you are getting from your durametic is the variation between cams on each bank and is an indicator of pad wear.

i'm running 5.? and 6.? right now and am going to continue racing. I think there is still lots of material on the pad so damaging the actual vario-cam isn't an issue, and I don't think that there is any chance of valves smacking cylinders yet so worst case minor loss of power. get it fixed? sure, eventually.
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Old 06-11-2013, 04:39 AM   #4
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Quote:
Originally Posted by jb92563 View Post
I hooked up a Durametric to my 2001 Boxster S and noticed that the Cam deviation was 6.4 on one bank and 4.7 on the other.

I think the specs allow 6 deviation so being that I'm out of spec I stopped racing.

Is this something I need to worry about, is being out of spec a serious issue with the engine timing?

For racing i'd rather bring it back into the good range and wonder what needs fixing in order to bring it back in line.

Any Ideas, suggestions?
Mine are almost exactly the same as yours. My 6.x deviation will go down to about 5.5 as the car warms up. 6 is supposedly the wear limit, but I have no drivability problems so I am just going to live with it.
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Old 06-11-2013, 06:30 AM   #5
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If the car is running well, has fresh fluids, and you are not finding bad things in the oil filter after each change... drive it like you stole it IMHO. It's easy to overthink Durametric data. Too much information for most of us Joes who don't really see a lot of cars on it and are not intimately familiar with what is ok vs what is serious trouble. Pretty soon everything looks like impending doom. It isn't.
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Old 06-12-2013, 11:32 AM   #6
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Understanding and interpreting the numbers is the key and biggest drawback of any monitoring device.

I don't have any driveability issues and perhaps the computer is able to compensate for the deviation in any case so perhaps just being overly paranoid about these mysterious numbers.

I'll do an oil change soon and see if there are any indications of trouble, then resume autocross racing if things are OK.
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